We propose to determine whether major modification of the known risk factors for atherogenesis alters the rate of progression of coronary arterial disease. In order to avoid the problems of clinical end points and large patient groups plaguing other clinical trials, we directly quantitate coronary arterial lesions using angiography and a computer graphics system which provides direct objective end points and small patient requirement. Patients who have had preoperative coronary arteriography and cornoary bypass surgery, but who have not had bypass of all major vessels will be enrolled. They will be randomly assigned to two groups: one to receive an aggressive multiple risk factor reduction program and the other to follow the usual care of their physicians. Those coronary vessels which had noncritical vascular lesions and were therefore not bypassed, provide the substrate for assessing the effectiveness of risk factor modification. Coronary angiography will be carried out prior to surgery and three years later. Computer quantitation of coronary luminal dimensions will provide a sensitive test of changes in coronary atherosclerosis. Two hundred forty patients will be randomized during the initial two years of the project. Clinical status and risk factors will be monitored at baseline and after one, two and three years in all participants. Those patients randomized to aggressive risk factor management will have close followup by study physicians and a "special intervention team." The resources of the Stanford Heart Disease Prevention will provide specialists in counseling, education programs and instructional materials for self-directed behavior change in the special intervention group. This study's major unique features are: 1) a randomized trial design, 2) the rate of change of coronary atherosclerosis as an end point rather than clinical variables, 3) highly reproducible computer quantitation of coronary atherosclerosis, 4) investigators experienced in long-term clinical intervention trials, 5) availability of the expertise and facilities for aggressive risk factor management, and 6) the use of a subset of patients for serial arteriography in whom restudy is clinically (and ethically) acceptable.